So, for a little background first, I went to school for graphics design. The kind for magazines and ad and similar.

The thing that annoys me to no end is seeing artists, those in the industry and otherwere, using DPI to refer to image resolution.
DPI is Dots Per Inch and it's a printer resolution, independent of image resolution.
Image resolution is measured in PPI or Pixels Per Inch.

So you saying an image is 300 DPI means nothing, since it's independant of actual image resolution. You can print a low resolution image, say 72 PPI at 1200 DPI, all that does is tell the printer how many dots to use when printing, nothing else.

The common thing to measure print quality when it comes to proffesional printing is LPI or Lines Per Inch, as a rule LPI is half PPI.
So to print an image in a newspaper, where the commonly used resolution is 85 LPI, you'd need an image resolution of 170 PPI.